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linux-next/security/keys/user_defined.c
David Howells cf7f601c06 KEYS: Add payload preparsing opportunity prior to key instantiate or update
Give the key type the opportunity to preparse the payload prior to the
instantiation and update routines being called.  This is done with the
provision of two new key type operations:

	int (*preparse)(struct key_preparsed_payload *prep);
	void (*free_preparse)(struct key_preparsed_payload *prep);

If the first operation is present, then it is called before key creation (in
the add/update case) or before the key semaphore is taken (in the update and
instantiate cases).  The second operation is called to clean up if the first
was called.

preparse() is given the opportunity to fill in the following structure:

	struct key_preparsed_payload {
		char		*description;
		void		*type_data[2];
		void		*payload;
		const void	*data;
		size_t		datalen;
		size_t		quotalen;
	};

Before the preparser is called, the first three fields will have been cleared,
the payload pointer and size will be stored in data and datalen and the default
quota size from the key_type struct will be stored into quotalen.

The preparser may parse the payload in any way it likes and may store data in
the type_data[] and payload fields for use by the instantiate() and update()
ops.

The preparser may also propose a description for the key by attaching it as a
string to the description field.  This can be used by passing a NULL or ""
description to the add_key() system call or the key_create_or_update()
function.  This cannot work with request_key() as that required the description
to tell the upcall about the key to be created.

This, for example permits keys that store PGP public keys to generate their own
name from the user ID and public key fingerprint in the key.

The instantiate() and update() operations are then modified to look like this:

	int (*instantiate)(struct key *key, struct key_preparsed_payload *prep);
	int (*update)(struct key *key, struct key_preparsed_payload *prep);

and the new payload data is passed in *prep, whether or not it was preparsed.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2012-10-08 13:49:48 +10:30

231 lines
4.9 KiB
C

/* user_defined.c: user defined key type
*
* Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/seq_file.h>
#include <linux/err.h>
#include <keys/user-type.h>
#include <asm/uaccess.h>
#include "internal.h"
static int logon_vet_description(const char *desc);
/*
* user defined keys take an arbitrary string as the description and an
* arbitrary blob of data as the payload
*/
struct key_type key_type_user = {
.name = "user",
.instantiate = user_instantiate,
.update = user_update,
.match = user_match,
.revoke = user_revoke,
.destroy = user_destroy,
.describe = user_describe,
.read = user_read,
};
EXPORT_SYMBOL_GPL(key_type_user);
/*
* This key type is essentially the same as key_type_user, but it does
* not define a .read op. This is suitable for storing username and
* password pairs in the keyring that you do not want to be readable
* from userspace.
*/
struct key_type key_type_logon = {
.name = "logon",
.instantiate = user_instantiate,
.update = user_update,
.match = user_match,
.revoke = user_revoke,
.destroy = user_destroy,
.describe = user_describe,
.vet_description = logon_vet_description,
};
EXPORT_SYMBOL_GPL(key_type_logon);
/*
* instantiate a user defined key
*/
int user_instantiate(struct key *key, struct key_preparsed_payload *prep)
{
struct user_key_payload *upayload;
size_t datalen = prep->datalen;
int ret;
ret = -EINVAL;
if (datalen <= 0 || datalen > 32767 || !prep->data)
goto error;
ret = key_payload_reserve(key, datalen);
if (ret < 0)
goto error;
ret = -ENOMEM;
upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
if (!upayload)
goto error;
/* attach the data */
upayload->datalen = datalen;
memcpy(upayload->data, prep->data, datalen);
rcu_assign_keypointer(key, upayload);
ret = 0;
error:
return ret;
}
EXPORT_SYMBOL_GPL(user_instantiate);
/*
* update a user defined key
* - the key's semaphore is write-locked
*/
int user_update(struct key *key, struct key_preparsed_payload *prep)
{
struct user_key_payload *upayload, *zap;
size_t datalen = prep->datalen;
int ret;
ret = -EINVAL;
if (datalen <= 0 || datalen > 32767 || !prep->data)
goto error;
/* construct a replacement payload */
ret = -ENOMEM;
upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
if (!upayload)
goto error;
upayload->datalen = datalen;
memcpy(upayload->data, prep->data, datalen);
/* check the quota and attach the new data */
zap = upayload;
ret = key_payload_reserve(key, datalen);
if (ret == 0) {
/* attach the new data, displacing the old */
zap = key->payload.data;
rcu_assign_keypointer(key, upayload);
key->expiry = 0;
}
if (zap)
kfree_rcu(zap, rcu);
error:
return ret;
}
EXPORT_SYMBOL_GPL(user_update);
/*
* match users on their name
*/
int user_match(const struct key *key, const void *description)
{
return strcmp(key->description, description) == 0;
}
EXPORT_SYMBOL_GPL(user_match);
/*
* dispose of the links from a revoked keyring
* - called with the key sem write-locked
*/
void user_revoke(struct key *key)
{
struct user_key_payload *upayload = key->payload.data;
/* clear the quota */
key_payload_reserve(key, 0);
if (upayload) {
rcu_assign_keypointer(key, NULL);
kfree_rcu(upayload, rcu);
}
}
EXPORT_SYMBOL(user_revoke);
/*
* dispose of the data dangling from the corpse of a user key
*/
void user_destroy(struct key *key)
{
struct user_key_payload *upayload = key->payload.data;
kfree(upayload);
}
EXPORT_SYMBOL_GPL(user_destroy);
/*
* describe the user key
*/
void user_describe(const struct key *key, struct seq_file *m)
{
seq_puts(m, key->description);
if (key_is_instantiated(key))
seq_printf(m, ": %u", key->datalen);
}
EXPORT_SYMBOL_GPL(user_describe);
/*
* read the key data
* - the key's semaphore is read-locked
*/
long user_read(const struct key *key, char __user *buffer, size_t buflen)
{
struct user_key_payload *upayload;
long ret;
upayload = rcu_dereference_key(key);
ret = upayload->datalen;
/* we can return the data as is */
if (buffer && buflen > 0) {
if (buflen > upayload->datalen)
buflen = upayload->datalen;
if (copy_to_user(buffer, upayload->data, buflen) != 0)
ret = -EFAULT;
}
return ret;
}
EXPORT_SYMBOL_GPL(user_read);
/* Vet the description for a "logon" key */
static int logon_vet_description(const char *desc)
{
char *p;
/* require a "qualified" description string */
p = strchr(desc, ':');
if (!p)
return -EINVAL;
/* also reject description with ':' as first char */
if (p == desc)
return -EINVAL;
return 0;
}